Transformation of bisphenol AF by chlorination: kinetic study and product identification

Bisphenols in indoor dust: A comprehensive review of global distribution, exposure risks, transformation, and biomonitoring

Bisphenols (BPs) are pervasive environmental contaminants extensively found in indoor environments worldwide. Despite their ubiquitous presence and potential health risks, there remains a notable gap in the comprehensive reviews focusing on BPs in indoor dust. Existing literature often addresses specific aspects such as exposure pathways, transformation products, or biomonitoring techniques, but lacks a consolidated, in-depth review encompassing all these facets. This review provides a comprehensive overview of the global distribution of BPs, emphasizing their prevalence in diverse indoor settings ranging from households and workplaces to public areas. Variations in BP concentrations across these environments are explored, influenced by factors such as industrial activities, consumer product usage patterns, and geographical location. Exposure assessments highlight ingestion, inhalation, and dermal contact as primary pathways for BP exposure, with ingestion being particularly significant for vulnerable groups such as infants and young children. Studies consistently reveal higher concentrations of BPs in urban indoor dust compared to rural settings, reflecting the impact of urbanization and intensive consumer practices. Moreover, BPs from mobile sources like vehicles contribute significantly to overall human exposure, further complicating exposure assessments. The review also delves into the transformation of BPs within indoor environments, emphasizing the diverse roles of physical, chemical, and biological processes in generating various transformation products (TPs). These TPs can exhibit heightened toxicity compared to their parent compounds, necessitating deeper investigations into their environmental fate and potential health implications. Critical examination of biomonitoring techniques for BPs and their metabolites underscores the importance of non-invasive sampling methods, offering ethical advantages and practicality in assessing human exposure levels. The emerging use of bioindicators, encompassing plants, animals, and innovative approaches like spider webs, presents promising avenues for effectively monitoring environmental contamination.

Responses of Vallisneria natans and Pistia stratiotes to Cu2+ and Mn2+ stress: Occurrence of caffeic acid and its degradation kinetics during chlorination

Macrophytes are crucial in maintaining the equilibrium of aquatic ecosystems. However, the pattern of macrophyte-derived caffeic acid (CA) release under heavy metal stress is yet to be fully understood. More importantly, due to its functional groups, CA may be a precursor to the formation of disinfection by-products, posing threats to water ecology and even safety of human drinking water. This study analyzed the responses of CA released by Vallisneria natans (V. natans) and Pistia stratiotes (P. Stratiotes) when exposed to Cu2+ and Mn2+ stress. Additionally, the CA levels in two constructed wetland ponds were detected and the degradation kinetics of CA during chlorination were investigated. Results indicated that CA occurred in two constructed wetland ponds with the concentrations of 44.727 μg/L (planted with V. natans) and 61.607 μg/L (planted with P. Stratiotes). Notably, heavy metal stress could significantly affect CA release from V. natans and P. Stratiotes. In general, under Cu2+ stress, V. natans secreted far more CA than under Mn2+ stress, the level could reach up to 435.303 μg/L. However, compared to V. natans, P. Stratiotes was less affected by Cu2+ and Mn2+ stress, releasing a maximum CA content of 55.582 μg/L under 5 mg/L Mn2+ stress. Aquatic macrophytes secreted more CA in response to heavy metal stresses and protected macrophytes from harmful heavy metals. CA degradation followed the pseudo first-order kinetics model, and the chlorination of CA conformed to a second-order reaction. The reaction rate significantly accelerated as NaClO, pH, temperature and Br- concentration increased. A new pathway for CA degradation and a new DBP 2, 2, 3, 3-tetrachloropropanal were observed. These findings pointed at a new direction into the adverse effect of CA, potentially paving the way for new strategies to solve drinking water safety problems.

Kinetics and mechanism of triclocarban degradation by the chlorination process: Theoretical calculation and experimental verification

Triclocarban (TCC) is an antimicrobial agent commonly used in many household and personal care products, and has been found persistent in the aquatic environment. Here we elucidate the kinetics and mechanism of TCC degradation during chlorination process by density functional theory (DFT) calculation and experimental verification. Results showed that hypochlorous acid (HOCl)/hypochlorite (OCl-) reacted with TCC via Cl-substitution, OH-substitution and C-N bond cleavage pathways. The reactivity of OCl- (2.80 × 10-7 M-1 s-1) with TCC was extremely low and HOCl (1.96 M-1 s-1) played the dominant role in TCC chlorination process. The N site of TCC was the most reactive site for chlorination. The second-order rate constants, which are determined using density functional theory (DFT) (kTCC-chlorineC, 1.96 M-1 s-1), can be separated into reaction rate constants related to the reactions of HOCl and OCl- with different isomers of TCC (TCC2 and TCC6). The obtained kTCC-chlorineC was consistent with the experimental determined second-order rate constant (kTCC-chlorineE, 3.70 M-1 s-1) in chlorination process. Eight transformation products (TP348, TP382, TP127, TP161, TP195, TP330, TP204, and TP296) were experimentally detected for chlorination of TCC, which could also be predicted by DFT calculation. Explicit water molecules participated in the chlorination reaction by transmitting the proton and connecting with TCC, HOCl/OCl- and other H2O molecules, and obviously reduced the energy barrier of chlorination.

Bisphenol A and its substitutes in the aquatic environment: Occurrence and toxicity assessment

Bisphenol A is classified as a high production volume chemical commonly used in the manufacture of polycarbonate plastics, epoxy resins and thermal paper. The endocrine disrupting properties of this xenobiotic have led to the restriction and prohibition of its use in many consumer products. To date, many chemical compounds with a chemical structure similar to bisphenol A have been used in consumer products as its replacement. The ubiquitous occurrence of bisphenol A and its substitutes in the environment and their endocrine activity as well as adverse effects on aquatic organisms is a global concern, especially because many available literature reports show that many substitutes (e.g. bisphenol AF, bisphenol AP, bisphenol B, bisphenol C, bisphenol F, bisphenol G, bisphenol FL, tetrabromobisphenol A) exert adverse effects on aquatic organisms, similar to, or even stronger than bisphenol A. Therefore, the objective of this paper is to provide a comprehensive overview of the production, sources, occurrence and associated toxicity, as well as the endocrine activity of bisphenol A and its substitutes on aquatic species. The environmental levels and ecotoxicological data presented in this review allowed for a preliminary assessment and prediction of the risk of bisphenol A and its substitutes for aquatic organisms. Furthermore, the data collected in this paper highlight that several compounds applied in bisphenol A-free products are not safe alternatives and regulations regarding their use should be introduced.